The annual average dose of radiation to which humans are exposed is 620 millirems. Government
standards allow those who work with radioactive material to be exposed to as much as 5,000
millirems per year.

Radiation amounts (expressed in millirems) associated with medical procedures and other
sources:

More Articles

A woman in her 20s returns to her dentist for her twice-annual checkup, which she never misses.
She takes good care of her teeth and hasn’t had the slightest sign of a cavity.

Still, a dental hygienist drapes a lead apron over her torso and positions bitewings in her
mouth for an annual round of X-rays.

Not so fast, some dentists would say. There’s a high probability the patient doesn’t need
them.

X-rays provide a good baseline for tracking decay and can help dentists identify problems that
can’t always be detected otherwise. And they deliver a radiation dose that’s one of the smallest
among medical diagnostic tests: about 0.5 millirems per procedure, roughly equivalent to the
radiation exposure you experience during an hourlong flight, according to the American Nuclear
Society.

Dental radiographs account for about 2.5 percent of the effective dose from medical radiographs
and fluoroscopies.

Still, new guidelines from the American Dental Association this month reiterate what dentists
have long known.

“Imaging is not a benign procedure,” said Dr. Paul Casamassimo, chief of dentistry at Nationwide
Children’s Hospital and a professor at Ohio State University’s College of Dentistry, who’s among
dentists advocating a reduction in radiation. He said, for example, that patients in their 20s who
receive routine dental care and show no signs of cavities probably could go five years between
X-rays.

The approach too many dentists take is skewed by training they received decades ago when tooth
decay was more prevalent, Casamassimo said. And then there’s “defensive dentistry,” fueled by fears
that a dentist might miss something, no matter how remote the possibility.

And “there’s probably some economic basis” that prompts some X-rays, Casamassimo said.

The ADA’s new recommendations for dental X-rays — the first update in eight years — is part of
an effort to reduce radiation exposure. The changes include updates to patient-shielding
recommendations, a new section on how to limit radiation exposure during radiographic examinations,
and new guidance on topics such as hand-held X-ray units.

The association cited a study of 490 patients that found that more-judicious use of dental
X-rays can result in a 43 percent reduction in the number of radiographs taken “without a
clinically consequential increase in the rate of undiagnosed disease.”

The association stressed that dentists remain in the best position to make decisions on whether
to prescribe X-rays after an oral exam or after considering a patient’s health history.

Dentists, like other professionals, aren’t always quick to embrace new guidelines, Casamassimo
said. But he said insurance companies could spur adoption of X-ray protocols recommended by the
ADA. For example, he said, health insurers could increasingly require dentists to perform risk
assessments to justify X-rays.

Dentists also can try to keep radiation dosages lower by switching from film to digital.
According to the ADA, digital imaging can further reduce the radiation dose by 40 to 60
percent.

“We’ve gotten so much better with the technology at reducing the actual dose,” said Dr. Angelo
Mariotti, a Columbus dentist and president of the Columbus Dental Society.X-rays remain the best
way to find cavities between teeth, he said. “We don’t have anything better at this time.”

Predetermined scheduling of X-rays long ago went by the wayside at many dentists’ offices, said
Dr. Matthew Messina, a dentist in a suburb of Cleveland. “We have not had an established routine
interval (for X-rays) for 20 years,” he said. “We’ve realized that you need to tailor patient care
to the individual needs of that patient.”

Patients sometimes question the need for X-rays. Messina said dentists need to be prepared to
share their rationale for an X-ray during those conversations and should be able to explain why
they believe the benefits outweigh the risks.